A 1-0 home defeat against Crystal Palace was followed by a 3-1 horror show at Barnsley in midweek but his men at least ended their losing streak and the 0-0 draw at Deepdale keeps them two points above Preston.
Goalkeeper Andy Lonergan denied Albion winger Graham Dorrans, the game's outstanding player, on three separate occasions and home defender Neill Collins also appeared to haul down Roman Bednar inside the penalty box in the second half.
However, Di Matteo was forced to concede his side have lost some of their sparkle after recording a thumping 5-0 win at Middlesbrough last month.
He said: "In the last three games we have picked up one point, which is not ideal.
"We had a bad week, which is a long time in football, but we are still okay.
"Maybe the good start we had at the beginning of the season gave the public a different level of expectation.
"But we know how hard it is to win games and you see that every week.
"We had a bad 45 minutes at Barnsley but we've played 11 games and there were a lot of minutes where we have played well."
In the 14th minute, Dorrans turned Preston defender Youl Mawene inside out before unleashing a fierce left-footed strike from 16 yards that Lonergan did superbly well to turn onto a post.
Bednar failed to hit the target from the rebound and Dorrans was left bitterly frustrated by Lonergan twice more in the closing stages.
In the 77th minute, more neat footwork from the Scot created the space to strike a fierce right-footed shot goalwards and Lonergan again reacted well to palm the ball to safety.
The home-grown stopper saved the best until last, reacting brilliantly to dive down low to his left to keep out Dorrans' powerful header in the fourth minute of added time.
Di Matteo added: "It seems that the opposition goalkeeper always plays well against us.
"But it's important that we create chances and Dorrans looked very sharp - he should have scored but he did well.
"We had the chances to win this game but Lady Luck wasn't on our side."
Preston boss Irvine again stated he was offered the chance to succeed Tony Mowbray at the Hawthorns before Di Matteo was appointed, despite claims to the contrary from the Baggies.
"I was offered the job - simple as that," he said.
"I am telling you I was offered the job and I didn't take it. I can only tell you what happened.
"They've got their own reasons for saying that."
On the game, Irvine added: "I don't think either team did enough to win or lose and it was a fair result.
"Lonergan wasn't called upon to make too many saves but the ones he did make were important."